Now, which of the photos was taken on the moon, and which on planet Earth? Yes, I know it's a stupid question: of course it's the photo on top - the iconic picture of Buzz Aldrin's footprint on the moon that was just making the rounds on the internet via various channels following Neil Armstrong's death last week.

The second picture was taken at 4050 m depth on the Porcupine Abyssal Plain, off the Irish continental margin. It remains a mystery to this day what created this pattern in the deep-sea sediment - the best bet is probably that it is the feeding pattern of an enteropneust (Acorn worm) which might be buried below the surface and coming up to feed. But, to my knowledge, nobody has any footage of this actually happening. If you are interested, I wrote about this photo – briefly – a while ago.

For the last few days, I've been intrigued by the thought that, although we – humans – have only been to the moon a few times, this image of the footprint is so significant that it is probably known to a very large proportion of the human population, if not the majority. At the same time, images of deep-sea mysteries can stay within a relatively small and exclusive circle for a long time. Or, looking at it another way: there's a human footprint on the moon while who knows what kind of weird, unknown and never-observed creatures hang out in the mud on the deep-sea floor of our very own planet.

The saying that "we know more about the surface of the moon than the deep sea" is quoted so often by deep-sea biologists and those reporting on deep-sea findings that it has almost become a cliché. To be honest, I am actually not sure that it is even true, not having looked much into what data we have on the surface of the moon – and, if we're just talking "surface", mapping of the deep-sea floor has of course been making steady progress over the last few decades and the maps are getting pretty good. But it is still true that much of the deep-sea floor remains unstudied concerning anything that matters, and also that big discoveries there have reliably been truly big, unexpected and exciting: hydrothermal vents or cold seeps anyone?

However, we now seem to have firmly entered into an era of moving beyond considerations of what's technically possible when it comes to our planet, our home, and going into action mode. Climate change needs to be addressed – and reduction of carbon dioxide emissions seems almost to be pushed to the back seat when it comes to options. Geoengineering has been discussed seriously for a while now, with some ideas such as iron fertilisation seemingly refusing to go away – which, if it worked, would affect the deep sea without anyone ever actually having looked seriously into what effects this might have on that environment.

Then there is the increasing scarcity of resources, including metals such as gold and copper. Can we think of any other place that we have not started mining yet? Oh yes – you guessed it – the deep sea! The situation is now such that a hiatus on the extraction of these metals from the deep-sea floor that lasted several decades seems to have ended, as recently described in this very news outlet.

And why not, you might say: deep-sea trawling, the increasing fisheries pressure on the Antarctic, or deep-sea oil drilling, to name a few random things, may be a much greater cause for concern. You may even be right. But before we start a whole new, big thing, we may first of all want to stop and consider the imprints we're leaving on this planet, and start taking an active interest in what's going on in these new exploitable areas, no matter how unseen or remote.